At present, various mobile operators perform promotions by way of price subsidies to attract mobile terminal users to use their networks. Particularly, a mobile operator sells mobile terminals to customers at prices below costs, or even presents mobile terminals to customers for free; meanwhile, such mobile terminals are locked to network of the mobile operator or are locked to mobile terminal cards sold by the mobile operator. That is to say, mobile terminals sold at prices below costs or presented have a network locking function.
A device is disclosed in the Chinese patent application entitled “Mobile Terminal Network Locking Device Based on Encryption chip”, published on Jan. 2, 2008 with the publication No. CN101098540A. As shown in FIG. 1, the device includes an encryption chip, a central processing unit and a user identification unit; wherein the encryption chip is serially connected between the central processing unit and the user identification unit, and configured to transfer and detect communication information between the central processing unit and the user identification unit. When the encryption chip detects the communication information including an International Mobile Subscriber Identification (IMSI) number that does not meet a network locking requirement from a mobile operator, the encryption chip interrupts the communication between the central processing unit and the user identification unit, to cause the mobile terminal unable to operate normally, that is, to perform the network locking function of the mobile terminal.
In terms of sales of mobile terminals, selling mobile terminals at prices below costs or presenting them for free is only one of many sales modes for mobile terminals, and other sales modes than the above sales mode do not require the mobile terminals to be sold to have the network locking function. However, during production of mobile terminals, it is obvious that, for a main board obtained by wiring according to the above patent application, wires between the central processing unit and the user identification unit of the main board are disconnected. If no encryption chip is connected, the central processing unit is unable to communicate with the user identification unit, then the mobile terminal is unable to operate normally. Therefore, for a mobile terminal which is manufactured without the network locking function, it is also necessary to arrange an encryption chip therein. However, for such a mobile terminal, in which no network locking requirement from the mobile operator is preset in the encryption chip, such that the network locking function is turned off. Obviously, this will leave the encryption chip unused, and as a result, hardware resources are wasted and costs are increased. Alternatively, a main board may be redesigned for a mobile terminal which do not need the network locking function, so as to connect the central processing unit and the user identification unit. However, in this way, expenses for designing, testing and verifying the main board are increased, and thus costs are increased.